1. Field of the Invention
The present invention relates to an image display apparatus used for electronic equipment including a display device having a plurality of light emitting elements, and relates to a driving method of the image display apparatus.
2. Description of the Related Art
Liquid crystal displays (LCDs) are commonly used as display devices in electronic equipment such as laptop computer and mobile phones.
Recently, organic electro-luminescent (EL) displays (organic light emitting diode (OLED) displays) have attracted attention as display devices capable of replacing LCDs.
OLED displays are self-light emitting display devices, like cathode ray tube (CRT) displays or plasma displays. In OLED displays, an anode electrode including indium tin oxide (ITO) is formed on a glass substrate, and an organic layer including a hole transport layer, a light emitting layer, and an electron transport layer, and a cathode electrode including a metal electrode are formed on the anode electrode.
Since OLED displays are self-light emitting devices, they consume power by emitting light. Power consumption is very low when black is displayed, and power consumption is maximum when white is displayed. Further, higher luminance display consumes a larger amount of power, and low luminance display only requires a small amount of power.
There is also a demand for reducing the size of portable terminals. Thus, the size of batteries is also reduced, and it is desirable that the portable terminals be operated for a long time by using a small amount of power. Therefore, there is a need to control power consumption.
Techniques for controlling power consumption of a display in a portable terminal are disclosed in, for example, Japanese Unexamined Patent Application Publication Nos. 2005-117172 and 2002-123208.
Japanese Unexamined Patent Application Publication No. 2005-117172 discloses an electronic apparatus configured to detect a remaining battery level and to control a luminance of a display when it is determined that the remaining battery level is low.
Japanese Unexamined Patent Application Publication No. 2002-123208 discloses an image display apparatus capable of changing a luminance and power consumption of a display and capable of adjusting the luminance and power consumption according to environmental conditions such as ambient brightness, a remaining battery level, content to be displayed, etc.
However, the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-117172 is an LCD technique, which has the following drawback. If the remaining battery level is low, luminance control is performed regardless of the type of images to be displayed on the display. Therefore, even dark images when displayed under low power consumption mode, may be displayed at a reduced luminance, which makes them hard to view.
In the technique disclosed in Japanese Unexamined Patent Application Publication No. 2002-123208, it is not specifically mentioned how to adjust the power consumption and luminance according to what type of content to be displayed on the display.
Therefore, there is a need to provide an image display apparatus and method that allows power consumption to be reduced while maintaining high image visibility.